The invention described herein relates generally to fluid flow controlling devices and more particularly to automatically operated valve mechanisms used with heat exchangers to govern the flow of fluid through the various passages thereof.
Internal combustion engines powered by a combustible petroleum gas are widely used. While such engines typically use gasoline as a fuel, it is well known that they may readily be converted to use petroleum fuels which are not liquids at or near room temperature and pressure. Examples of such fuels are LPG (liquefied petroleum gas) which comprises a mixture of hydrocarbons which are gases or vapors at engine inlet pressures and temperatures, methane, ethane, propane, butane, as well as mixtures thereof. Such fuels are liquefied and stored under high pressure prior to use.
Although they provide somewhat less energy than gasoline, such liquefied gases are also less expensive than gasoline. Indeed, the spread in price between the two types of fuel has recently made the use of certain liquefied gases, and in particular, propane, quite attractive.
The conversion of a liquefied gas, such as liquefied propane, to a vapor by expansion for purposes of carburetion in an internal combustion engine results in a significant refrigerant action which would quickly cause the system to ice up and freeze if heat were not added. The art teaches that this problem may be controlled by converting the liquid propane to its vapor in a heat exchanger wherein the necessary heat is supplied by the heated coolant liquid used to cool the engine. Unfortunately, the amount of heat supplied to the exchanger by constant circulation of the coolant liquid through the exchanger is highly variable and depends on a wide variety of factors such as engine thermostat, engine and water pump r.p.m., ambient temperature, ventilation, emission controls, and time required to reach the desired coolant operating temperature for the engine.
Any substantial variation in the amount of heat supplied to the heat exchanger for vaporizing the liquid propane can result in a significant change in the expansion rate of the propane as it vaporizes. This in turn can result in large variations in the fuel/air ratio in the carburetor and a fuel/air mixture that may be either too lean or too rich for the particular operating conditions.
Moreover, in recent years governmental (EPA) regulations have required engine coolants in the coolant jacket to be at temperatures as high as 212.degree. F. to reduce engine exhaust emissions. Unfortunately, however, when propane vapor is heated in excess of about 140.degree. F. it begins to "crack" and forms a liquid oily residue which adversely affects the elastomeric components and seals in the system.
It will thus be seen that it is highly advantageous to have some means of closely controlling or regulating the flow of engine coolant through the heat exchanger to thereby control the amount of heat which is added to the propane. In U.S. Pat. No. 3,378,063 issued Apr. 16, 1968, R. L. Mefferd teaches a thermostat control valve designed to control such flow. Unfortunately, the valve taught by Mefferd is expensive to manufacture and is not self cleaning. It requires the use of a cage valve as opposed to the simpler poppet valve.
Accordingly, an object of the present invention is to provide a novel thermostatically controlled valve for regulating a flow of heated fluid, e.g., engine coolant.
Another object of the invention is to provide a more economic thermostatically controlled valve for regulating the vaporization of liquefied petroleum gases such as, for example, propane.
Yet another object of the invention is to provide a thermostatically controlled valve for regulating the vaporization of liquefied petroleum gases which is self cleaning.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.